Sea Noise Research Articles

Background Noise Measurements at the Sea Horizon

The design of passive infrared detection systems requires a knowledge of the sea-horizon background noise. The horizontal wave-number distribution of noise from the sky immediately above and the sea immediately below the horizon was measured during 1956 and 1957. The measurements, which are discussed in this paper, included the range of wave numbers from 7.1 to 91 cycles/rad. The results are graphed in terms of the one-dimensional angular Wiener spectrum of the background noise as a function of the horizontal wave number and show that both the sky and sea noise spectra are inversely proportional to the 1.7 power of the wave number in the region from 14 to 91 cycles/rad. A brief discussion of the analyzing equipment is also included.

Sonobuoyによる海中騒音および魚群の水中音の検知(日本航海学会第21回講演会)

The research of sea noise in the ocean or the detection of fish shoal by their swimming sound were usually made by research vessels, or, in case of set net fishing, by the line transmission of under water sound to coastal receiving stations by means of electric cable. For the purpose of listening to the sea noises of several locations simultaneously or surveying the fish location by the sound originated from fish shoal, it has been demonstrated that the "sonobuoy's disposition offers an easier and more economic survey. The observation is made by setting several sonobuoys at sea and receiving the under water sound transmitted through the radio system of a coastal station. The sonobuoy device consists of hydrophone, audio-amplifier, radio transmitter and receiver, speaker, pen-recorder and two channel magnetic tape-recorder. The sonobuoy adopts frequency modulation system at V.H.F. of 42.M.C. band and its effective communication range is up to 10km. The under water signal caught by speaker is recorded on pen-recorder or on magnetic tape-recorder. The observation by this device of the swimming sound of yellowtail in set-net fishing grounds has demonstrated that the sonobuoy can clearly distinguish the sound of yellowtail from the sea noise, and that the frequency of sound generation at the entrance of set-net has a certain relation with probable catch of fish. It is expected in future that we can tell the possibility of catch by listening to the sound of fish by means of this device. We can conclude that in feature, the forecast of fish catch may be possible by listening the sound of fish.